When the ego refuses to acknowledge anxiety-producing realities, this is the defense mechanism known as

This is the defense mechanisms known as denial.

Explanation:

A defense mechanism is an unconscious process which occurs when an individual cannot handle the stress and anxiety induced by his/her reality and needs to protect him/herself from it.

Denial is a type of defense mechanism in which the individual refuses to accept his/her reality and thus blocks external events which can damage his/her conscience. In this case, he/she can be seen in complete denial and thus acts as if certain things, events or aspects do not exist.

Arteries and veins

Explanation:

Xylem and phloem ,vein and arteries both carry nutrient and mineral in the plant and animal.